1Ppmbrighten User Manual(0)                          Ppmbrighten User Manual(0)
2
3
4

NAME

6       ppmbrighten - change a PPM image's Saturation and Value
7
8

SYNOPSIS

10       ppmbrighten  [-normalize] [-saturation [+|-saturation_percent]] [-value
11       [+|-value_percent]] ppmfile
12
13       Minimum unique abbreviation of option is acceptable.  You may use  dou‐
14       ble  hyphens  instead  of single hyphen to denote options.  You may use
15       white space in place of the equals sign to separate an option name from
16       its value.
17
18

DESCRIPTION

20       This program is part of Netpbm(1).
21
22       ppmbrighten  increases  or decreases the Saturation and Value (from the
23       HSV color space) of each pixel of a PPM image.   You  specify  the  per
24       centage change for each of those parameters.
25
26       You  can  also remap the colors of the pixels so their Values cover the
27       full range of possible Values.
28
29       Hue-Saturation-Value, or HSV, is one way to represent a color, like the
30       more  well-known  RGB.   Hue,  Saturation, and Value are numbers in the
31       range from 0 to 1.  We always capitalize them in this document when  we
32       mean the number from the HSV color space, especially since "value" as a
33       conventional English word has a much more abstract meaning.
34
35       Value is a measure of how bright the color is, relative to some  speci‐
36       fied  maximum  (the  PPM format is also defined in terms of a specified
37       maximum brightness -- For the purposes of this program,  they  are  the
38       same).   In  particular,  it is the brightness of the brightest primary
39       color component of the color divided by the maximum brightness possible
40       for a component.  Zero Value means black.  White has full Value.
41
42       Hue  is  an  indication of the secondary color with the same brightness
43       that most closely approximates the color.  A secondary color is made of
44       a combination of at most two of the primary colors.
45
46       Saturation  is  a  measure of how close the color is to the color indi‐
47       cated by the Hue and Value.  A lower number means  more  light  of  the
48       third primary color must be added to get the exact color.  Full Satura‐
49       tion means the color is a secondary color.  Zero Saturation  means  the
50       color  is  gray  (or  black  or white).  Decreasing the saturation of a
51       color tends to make it washed out.
52
53       If it is impossible to increase the Value of a pixel by the amount  you
54       specify  (e.g.  the  Value  is  .5  and you specify +200%), ppmbrighten
55       increases it to full Value instead.
56
57       If it is impossible to increase the Saturation of a pixel by the amount
58       you  specify (e.g. it is already half saturated and you specify +200%),
59       ppmbrighten increases it to full Saturation instead.
60
61       For a simpler kind of brightening, you can use pamfunc -multiplier sim‐
62       ply  to  increase the brightness of each pixel by a specified per cent‐
63       age, clipping each RGB component where the calculated brightness  would
64       exceed  full brightness.  Thus, the brightest colors in the image would
65       change chromaticity in addition to not getting the specified brightness
66       boost.   For decreasing brightness, pamfunc should do the same thing as
67       ppmbrighten.
68
69       ppmflash does another kind of brightening.  It  changes  the  color  of
70       each  pixel  to bring it a specified per centage closer to white.  This
71       increases the value and saturation.
72
73

EXAMPLES

75       To double the Value of each pixel:
76       ppmbrighten -v 100
77
78       To double the Saturation and halve the Value of each pixel:
79       ppmbrighten -s 100 -v -50
80
81

OPTIONS

83       -value value_percent
84              This option specifies the amount, as a per centage, by which you
85              want to change the Value of each pixel.  It may be negative.
86
87
88       -saturation value_percent
89              This option specifies the amount, as a per centage, by which you
90              want to change the Saturation of each pixel.  It  may  be  nega‐
91              tive.
92
93
94
95       -normalize
96              This  option  causes ppmbrighten to linearly remap the Values of
97              the pixels to cover the range 0 to 1.  The option name is  wrong
98              --  this  operation  is not normalization (it was named in error
99              and the name has been kept for backward compatibility).
100
101              ppmbrighten applies the brightening that you  specify  with  the
102              -value option after the remapping.
103
104              Before  Netpbm  10.14  (March  2003),  your input must be from a
105              seekable file (not a pipe) to use -normalize.  If it isn't,  the
106              program fails with a bogus error message.
107
108
109
110

SEE ALSO

112       pnmnorm(1),    ppmdim(1),    pamfunc(1),    ppmflash(1),   pamdepth(1),
113       pnmgamma(1), ppmhist(1), ppm(1)
114
115

AUTHOR

117       Copyright (C)  1990  by  Brian  Moffet.   Copyright  (C)  1989  by  Jef
118       Poskanzer.
119
120       Permission  to  use, copy, modify, and distribute this software and its
121       documentation for any purpose and without fee is hereby  granted,  pro‐
122       vided  that  the  above  copyright notice appear in all copies and that
123       both that copyright notice and this permission notice  appear  in  sup‐
124       porting  documentation.   This  software  is  provided  "as is" without
125       express or implied warranty.
126

DOCUMENT SOURCE

128       This manual page was generated by the Netpbm tool 'makeman'  from  HTML
129       source.  The master documentation is at
130
131              http://netpbm.sourceforge.net/doc/ppmbrighten.html
132
133netpbm documentation            26 October 2012     Ppmbrighten User Manual(0)
Impressum